Key Laboratory of Animal Diseases Diagnostic and Immunology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China.
Key Laboratory of Animal Diseases Diagnostic and Immunology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China
J Virol. 2018 Jul 17;92(15). doi: 10.1128/JVI.00366-18. Print 2018 Aug 1.
Porcine reproductive and respiratory syndrome virus (PRRSV), a virulent pathogen of swine, suppresses the innate immune response and induces persistent infection. One mechanism used by viruses to evade the immune system is to cripple the antigen-processing machinery in monocyte-derived dendritic cells (MoDCs). In this study, we show that MoDCs infected by PRRSV express lower levels of the major histocompatibility complex (MHC)-peptide complex proteins TAP1 and ERp57 and are impaired in their ability to stimulate T cell proliferation and increase their production of CD83. Neutralization of sCD83 removes the inhibitory effects of PRRSV on MoDCs. When MoDCs are incubated with exogenously added sCD83 protein, TAP1 and ERp57 expression decreases and T lymphocyte activation is impaired. PRRSV nonstructural protein 1α (Nsp1α) enhances CD83 promoter activity. Mutations in the ZF domain of Nsp1α abolish its ability to activate the CD83 promoter. We generated recombinant PRRSVs with mutations in Nsp1α and the corresponding repaired PRRSVs. Viruses with Nsp1α mutations did not decrease levels of TAP1 and ERp57, impair the ability of MoDCs to stimulate T cell proliferation, or increase levels of sCD83. We show that the ZF domain of Nsp1α stimulates the secretion of CD83, which in turn inhibits MoDC function. Our study provides new insights into the mechanisms of immune suppression by PRRSV. PRRSV has a severe impact on the swine industry throughout the world. Understanding the mechanisms by which PRRSV infection suppresses the immune system is essential for a robust and sustainable swine industry. Here, we demonstrated that PRRSV infection manipulates MoDCs by interfering with their ability to produce proteins in the MHC-peptide complex. The virus also impairs the ability of MoDCs to stimulate cell proliferation, due in large part to the enhanced release of soluble CD83 from PRRSV-infected MoDCs. The viral nonstructural protein 1 (Nsp1) is responsible for upregulating CD83 promoter activity. Amino acids in the ZF domain of Nsp1α (L5-2A, rG45A, G48A, and L61-6A) are essential for CD83 promoter activation. Viruses with mutations at these sites no longer inhibit MoDC-mediated T cell proliferation. These findings provide novel insights into the mechanism by which the adaptive immune response is suppressed during PRRSV infection.
猪繁殖与呼吸综合征病毒（PRRSV）是一种猪的烈性病原体，它能抑制先天免疫反应并诱导持续性感染。病毒逃避免疫系统的一种机制是削弱单核细胞衍生树突状细胞（MoDC）中的抗原加工机制。在这项研究中，我们表明，被 PRRSV 感染的 MoDC 表达较低水平的主要组织相容性复合体（MHC）-肽复合物蛋白 TAP1 和 ERp57，并且其刺激 T 细胞增殖和增加 CD83 产生的能力受损。中和 sCD83 去除了 PRRSV 对 MoDC 的抑制作用。当 MoDC 与外源性添加的 sCD83 蛋白孵育时，TAP1 和 ERp57 的表达下降，T 淋巴细胞的激活受到损害。PRRSV 非结构蛋白 1α（Nsp1α）增强 CD83 启动子活性。Nsp1α 的 ZF 结构域中的突变使其丧失激活 CD83 启动子的能力。我们生成了具有 Nsp1α 突变的重组 PRRSV 及其相应修复的 PRRSV。具有 Nsp1α 突变的病毒不会降低 TAP1 和 ERp57 的水平，不会损害 MoDC 刺激 T 细胞增殖的能力，也不会增加 sCD83 的水平。我们表明，Nsp1α 的 ZF 结构域刺激 CD83 的分泌，这反过来又抑制 MoDC 功能。我们的研究提供了 PRRSV 免疫抑制机制的新见解。PRRSV 在全球范围内对养猪业造成了严重影响。了解 PRRSV 感染抑制免疫系统的机制对于建立强大和可持续的养猪业至关重要。在这里，我们证明 PRRSV 感染通过干扰 MHC-肽复合物中蛋白质的产生来操纵 MoDC。该病毒还由于 PRRSV 感染的 MoDC 增强释放可溶性 CD83，从而损害 MoDC 刺激细胞增殖的能力。病毒非结构蛋白 1（Nsp1）负责上调 CD83 启动子活性。Nsp1α 的 ZF 结构域中的氨基酸（L5-2A、rG45A、G48A 和 L61-6A）对于 CD83 启动子的激活至关重要。这些位点发生突变的病毒不再抑制 MoDC 介导的 T 细胞增殖。这些发现为 PRRSV 感染期间适应性免疫反应被抑制的机制提供了新的见解。
